Thrombin activatable fibrinolysis inhibitor inhibits fibrinolysis by removing C-terminal lysine residues from partially degraded fibrin. It is expressed by the liver and circulates in plasma as a zymogen TAFI, which can be activated to an active carboxypeptidase, TAFIa, by plasmin or thrombin. Thrombomodulin in complex with thrombin increased the activation 1250-fold. The active carboxypeptidase TAFIa is unstable with a half-life of about 10 min at 37 °C and is inactivated to TAFIai by conformational change.